Only build and show concept tree pertaining to requested scheme

[jacobtylerwalls]

When visiting the route for a scheme, we build the concept tree for every scheme, show them, and just highlight the requested one.

We should only build(*) the concept tree for the requested scheme and just show that one scheme's concepts.

(*) Given how indirectly the concept data is stored, it might be fine to just continue building all schemes on the first request, and just make sure to only serialize out the requested one -- OR we could change how the concept builder queries tiles to filter down on the part_of_scheme tile, and then cache those concept trees individually, but performance issues can be surprising, so we might want to measure both approaches in case the part_of_scheme lookup is costly.

[jacobtylerwalls]

@chrabyrd points out we should revisit the drawer/splitter decision as part of this design.